*sigh* I hate this too. the Kingdom of Andalusia can only be formed by an Arabic Culture Group. Technically speaking, only the someone with is of Arabic culture should be able to hold it. Therefore, you can't pass it on to non-Arabs.
It's like why the Kingdom of Portugal can only be formed by Christians.
Making it only formable by a certain culture (group) is one thing, but once it exists and already is owned by someone of a different culture handing it out should perhaps be possible.
Furthermore IIRC Andalusia used to be only formable by Muslims.